Flight compensation glossary

A

ADR — Alternative Dispute Resolution

Independent, binding-on-the-airline complaint scheme that handles flight-compensation disputes for UK261 cases. UK carriers must subscribe to one. The two main UK schemes are CEDR and AviationADR. Free to passengers; decisions bind the airline but not the passenger.

ADS-B — Automatic Dependent Surveillance–Broadcast

The radio system every modern aircraft uses to broadcast its position, altitude, speed and identity. The data is free and public, which is why services like FlightAware, Flightradar24 and ClaimBox can verify in real time exactly when your plane took off and landed — the same evidence the airline uses internally.

Article 7

The provision of EU261/UK261 that sets the fixed compensation amounts (€250/€400/€600 or £220/£350/£520). When you write a claim, you'll cite "Article 7" as the legal basis for the amount you're demanding.

Article 9

The "duty of care" provision of EU261/UK261. Requires the airline to provide meals, communications, hotel and ground transport during a long delay or cancellation — even when extraordinary circumstances exempt them from cash compensation.

Automatic refund rule

The colloquial name for the US DOT requirement under 14 CFR §259.5 that airlines refund cancelled or significantly changed flights in cash, to the original payment method, without the passenger having to ask. Effective 28 October 2024.

B

BMVI

Bundesministerium für Digitales und Verkehr — the German federal ministry that enforces EU261 for flights departing Germany. One of the EU's national enforcement bodies; passengers escalate German-airline claims here.

Bumping

US-English shorthand for involuntary denied boarding, usually because the flight is overbooked. Under EU261/UK261 Article 4, the airline owes the same €250/€400/€600 (or £220/£350/£520) regardless of whether they later rebook you.

C

CAA — Civil Aviation Authority (UK)

The UK regulator that enforces UK261. Its Passenger Advice and Complaints Team (PACT) handles passenger escalations free of charge.

Cancellation

The non-operation of a flight that was previously scheduled and on which at least one place was reserved. Triggers EU261/UK261 compensation if announced less than 14 days before departure (with intermediate exceptions). Triggers automatic refund under US DOT.

CEDR

The Centre for Effective Dispute Resolution — one of the two UK ADR providers for airline disputes. Binding on the airline.

CJEU

Court of Justice of the European Union. Its rulings on EU261 (Sturgeon, Wallentin-Hermann, Pešková, Krüsemann, etc.) define how the regulation is interpreted across the EU. Retained-EU-case-law principles mean UK courts still follow these.

Claim packet

The bundle of documents an airline needs to process a compensation claim: cover letter citing the regulation, calculated amount, booking reference, boarding pass, evidence of delay (cabin-door-open time vs. scheduled), receipts for expenses. ClaimBox assembles this automatically.

COC — Contract of Carriage

The legal contract between the airline and the passenger. US airlines publish their COCs on their websites; they set out the airline's commitments above and beyond statutory rules — especially relevant for US DOT controllable-delay benefits.

COD — Cancelled, Outbound Disruption

Airline-internal code used in operational systems for a cancelled outbound flight. You'll occasionally see it on baggage tags or screenshots from gate agents — it just means "this flight was cancelled."

Code-share

An arrangement where a flight is marketed under one airline's flight number but operated by another. For EU261/UK261, the operating carrier owes the compensation, not the marketing carrier. Your ticket may say "Delta" but if the airframe and crew are KLM's, KLM pays.

Controllable delay

A US DOT term for a delay caused by something within the airline's control — mechanical issues, crew availability, IT outages. Triggers airline-specific commitments tracked on the DOT Cancellation and Delay Dashboard.

D

Denied boarding

Refusal by the airline to transport a passenger who holds a confirmed reservation and presents for boarding on time. Almost always due to overbooking. Triggers EU261/UK261 compensation at the standard amounts.

Distance band

The three EU261 / four UK261 distance categories that determine the compensation amount. EU261: up to 1,500 km; 1,500–3,500 km; over 3,500 km (intra-EU); over 3,500 km (EU↔non-EU). UK261 adds an over-3,500 km 3–4 hour band at £260.

DOT — Department of Transportation (US)

The US federal department whose Office of Aviation Consumer Protection (OACP) enforces 14 CFR Part 259 and handles passenger complaints. Free to file; can fine airlines for non-compliance.

Duty of care

EU261/UK261 Article 9 obligation: meals, two free communications, hotel if overnight, and transport to it — provided during a long delay or cancellation, regardless of cause. Survives the extraordinary-circumstances defence.

E

EU261

Regulation (EC) No 261/2004 — the EU law that requires airlines to pay €250–€600 for long delays, short-notice cancellations and denied boarding. In force since 17 February 2005. Covers flights departing the EU on any airline and flights arriving in the EU on EU-licensed airlines.

Extraordinary circumstances

The EU261/UK261 defence under Article 5(3) that exempts the airline from cash compensation when the disruption was caused by genuinely external events the airline could not reasonably prevent: severe weather that shuts the route, air-traffic-control strikes, bird strikes, security threats, hidden manufacturer defects. Read narrowly by EU and UK courts; the burden of proof is on the airline.

G

Great-circle distance

The shortest distance between two points on the surface of a sphere. EU261 and UK261 use great-circle distance from departure to final destination (not the sum of legs) to determine the compensation amount.

I

IROP — Irregular Operation

Airline-internal term for any disruption to the planned schedule — cancellation, diversion, long delay, equipment swap. When you see "IROP team" or "IROP rebooking," that's the airline's operational response process. From the passenger's side, an IROP usually means EU261/UK261 or US DOT rights are in play.

K

Krüsemann ruling

CJEU case C-195/17 (April 2018): wildcat cabin-crew strikes are not extraordinary circumstances under EU261. The airline is responsible for industrial relations with its own staff. Important precedent — many airlines still cite their own strikes as extraordinary and get rejected.

L

Limitation period

The legal deadline within which a claim must be filed. UK: 6 years in England/Wales/NI (5 in Scotland) under the Limitation Act 1980. Germany: 3 years. France: 5. Netherlands: 2. Montreal Convention claims: 2 years.

M

Montreal Convention 1999 (MC99)

International treaty governing airline liability for international flights — death, injury, baggage, and consequential losses caused by delay. Caps liability at 1,519 SDR for baggage (as of 28 Dec 2024), 5,346 SDR for delay-caused losses, and 151,880 SDR for death/injury. Applies on top of EU261/UK261/US DOT for international flights.

N

NEB — National Enforcement Body

Each EU member state designates one body responsible for enforcing EU261. Passengers escalate rejected EU261 claims to the NEB of the country of departure (or, for inbound EU-carrier flights, of the carrier's country). The European Commission maintains the official list.

O

OACP — Office of Aviation Consumer Protection

The US DOT office that enforces 14 CFR Part 259 and handles airline passenger complaints. Submissions at transportation.gov/airconsumer/file-consumer-complaint.

Operating carrier

The airline that actually operates the flight (the airframe and crew). Under EU261/UK261 the operating carrier owes the compensation, not the marketing carrier whose name is on the ticket.

Overbooking

The practice of selling more seats than the aircraft has, on the assumption some passengers will no-show. When everyone shows up, the airline must first ask for volunteers; if not enough volunteer, it involuntarily denies boarding to others — who are owed denied-boarding compensation under EU261/UK261 Article 4 or US DOT Part 250.

P

PACT

The UK CAA's Passenger Advice and Complaints Team — the team that handles UK261 escalations when an airline rejects a valid claim.

Pešková ruling

CJEU case C-315/15 (May 2017): bird strikes are extraordinary circumstances under EU261. The airline isn't liable for a delay caused by hitting a bird, even if it had to inspect or repair the aircraft afterwards.

R

Refund

The return of your ticket price. EU261/UK261 Article 8 gives you the choice between refund and rerouting on any cancellation. US DOT now requires automatic cash refund (not voucher) under 14 CFR §259.5 when you don't fly.

Rerouting

Alternative transport to your destination, offered by the airline as an alternative to refund on a cancellation. Must be at the earliest opportunity or at a later date of your choosing, subject to seat availability.

S

SDR — Special Drawing Right

The IMF's reserve currency unit. The Montreal Convention denominates its liability limits in SDR, which are recalculated every five years for inflation. As of 2026, 1 SDR ≈ US$1.34; the baggage limit is 1,519 SDR (~$2,000).

Significant change

The US DOT term defining what counts as a sufficient schedule change to trigger the automatic refund right. 3+ hours domestic, 6+ hours international, airport change, added connection, downgrade, or accessibility-affecting change.

Significantly delayed baggage

Under 14 CFR §259.5, baggage that arrives 12+ hours late on a domestic flight, or 15–30 hours late on an international flight (varies by flight length). Triggers automatic refund of any baggage fees paid.

Sturgeon ruling

CJEU case C-402/07 (November 2009): a 3+ hour arrival delay triggers the same fixed compensation as a cancellation under EU261, even though the regulation as drafted only paid for cancellations. The single most important ruling in EU passenger rights.

T

Through booking

A single ticket covering multiple connecting flights. EU261/UK261 compensation applies to the final-destination arrival on a through booking — even if the qualifying delay happened on an earlier leg. Separate tickets break this protection.

U

UK261

The post-Brexit UK retention of EU261, codified by The Air Passenger Rights (EU Exit) Regulations 2019. Pays £220–£520; enforced by the UK CAA. Substantively identical to EU261 in everything except currency and enforcement body.

V

Voucher

A travel credit offered instead of a cash refund. Under EU261/UK261, vouchers are only valid if the passenger accepts them in writing — the default is cash compensation. Under US DOT 14 CFR §259.5, same rule applies: cash is the default, vouchers only if you affirmatively choose them.

Definitions are general guidance, not legal advice. Specialised terms may have airline- or jurisdiction-specific nuances. Always confirm with the relevant regulator or counsel.